23. Ethnicity-Dependent and Independent Heterogeneity in Healthy Normal Breast Hierarchy Impacts Tumor Characterization

Nakshatri, H. et al. 2015

Ethnicity and genetics are partly responsible for “heterogeneity,” or the genetic differences from one area of tissue to another. These differences may show up as different types of cells or mutations of the cells themselves.

For this research, scientists wanted to explore heterogeneity in normal breast tissue, breast cancer tissue and tissue adjacent to breast cancer tumors. By looking at ethnicity and genetics, they hoped to identify markers that could shed light on why women of different ethnicities or genetic predispositions develop certain types of breast cancer. 


The scientists looked at cells from 60 primary breast tissues, including 25 healthy donors from the Komen Tissue Bank. They subjected all the samples to the same conditions and to the same examination in the lab.


The researchers identified two types of cells that are enriched in women of African American ancestry and specific defects in cells from BRCA1 (a genetic mutation) carriers. They also found differences in normal and tumor-adjacent tissues in the same individual. Even normal breast tissue was found to have great heterogeneity, which scientists think may be partially influenced by ethnicity.

They saw differences in the types of genetic markers among African American and Caucasian women, suggesting that ethnicity may have an effect on the expression of these markers.

What this study is important:

When determining breast cancer risk, researchers are finding many indicators at the cellular and genetic levels, some of which are due to ethnicity or genetic predisposition. This study found several differences in the types and amounts of markers between Caucasian and African American women, and among women with genetic mutations and women without them. All of these findings may help estimate risk according to individuals’ cellular and genetic makeup.